Batteries capacity measure

c_joerg

1237

« on: 01 / August / 2016, 07:17:29 »

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Hello,
I have a couple of NB-10L batteries. Is there any way with CHDK to measure the capacity? For time-lapse I want to know, which is my best Akku. It’s not necessary to know the absolute value of the capacity, but would be interesting. The easiest way would be if I could measure the batteries current like the batteries voltage but I think that’s not possible or?

Another idea is, to measure the current with my external power supply in playback mode with a fixed picture. Then I would start a script in playback mode which logs the voltage over time. After the run I could nearly calculate the Batteries capacity.

Does anybody else has another solution?

Great Joerg

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waterwingz

12130

Re: Batteries capacity measure

« Reply #1 on: 01 / August / 2016, 08:07:35 »

Quote from: c_joerg on 01 / August / 2016, 07:17:29

I have a couple of NB-10L batteries. Is there any way with CHDK to measure the capacity? For time-lapse I want to know, which is my best Akku. It’s not necessary to know the absolute value of the capacity, but would be interesting. The easiest way would be if I could measure the batteries current like the batteries voltage but I think that’s not possible or?

Another idea is, to measure the current with my external power supply in playback mode with a fixed picture. Then I would start a script in playback mode which logs the voltage over time. After the run I could nearly calculate the Batteries capacity.

Measuring current draw does not tell you anything about a battery's capacity. Current draw is determined by what the camera needs and it will actually appear to go up as the battery voltage droops !

The only thing you can do is measure the time to a fixed voltage droop as the capacity nears exhaustion. The battery with the longest time has the most holding capacity.

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c_joerg

1237

Re: Batteries capacity measure

« Reply #2 on: 01 / August / 2016, 08:41:27 »

Quote from: waterwingz on 01 / August / 2016, 08:07:35

Measuring current draw does not tell you anything about a battery's capacity.

Why not?
May be the cam needs in playback mode 500mA und the cam run 2h then the capacity would be around 1000mAh.
I would think that the current in playback mode is nearly constant (may be +-10%). If I do one measurement with external power supply, this might be correct enough.

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M100 100a, M3 121a, G9x II (1.00c), 2*G1x (101a,100e), S110 (103a), SX50 (100c), SX230 (101a), S45,
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waterwingz

12130

Re: Batteries capacity measure

« Reply #3 on: 01 / August / 2016, 09:19:41 »

Correct. I'll clarify my previous statement. Measuring current draw tells you nothing much about a battery's capacity. Measuring the time that a battery can draw a set amount of current does.

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c_joerg

1237

Re: Batteries capacity measure

« Reply #4 on: 05 / December / 2016, 03:50:12 »

I would like to share the results of my measurements.

How did I perform the measurement:
- Camera in playback mode (gray image)
- Display brightness on 2/5
- Measurement of current via DC coupler (mean value)
- Measurement of the time in the playback mode via a script.
- capacity = current (mean value) * time

Interestingly, all the spare batteries (except for HAMA) had no temperature sensor.

NB-10L
Canon I (920mAh, 3-4years old) => 910mAh
Canon II (920mAh,3-4years old) => 860mAh
Canon III (920mAh, 3-4years old) => 908mAh
Hama (820mAh, 1-2years old) => 836 mAh
Baxxtar (950mAh, 1-2years old) => 972mAh
2 * No Name died in less than 2 years capacity < 100mAh

NB-5L
Canon (1120mAh, 4years old) => 990mAh
No Name I (1200mAh, 5month old) => 680mAh
No Name II (1200mAh, 5month old) => 700mAh

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M100 100a, M3 121a, G9x II (1.00c), 2*G1x (101a,100e), S110 (103a), SX50 (100c), SX230 (101a), S45,
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jmac698

131

Re: Batteries capacity measure

« Reply #5 on: 28 / January / 2017, 00:01:33 »

Thanks for posting your results. I was aware that off-brand batteries would have less capacity, but I just needed something that works for now. I noticed something, my universal charger says it's NiCD, not Li-Ion. Another test I could run, is compare the voltage dischage curve. Luckily I have this plotted from the old battery.

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